Telephone-transmitter



(No Model.)

P. BLAKE.

TELEPHONE TRANSMITTER. No. 357,452. Patented Feb. 8, 1887.-

N. PETERS. Plmwuxho n her. Washington D. C.

UNITED STATES PATENT @FFiCEO FRANCIS BLAKE, OF VVES'ION, ASSIGNCR TO THEAMERICAN BELL TELE- PHONE COMPANY, OF BOSTON, MASSACHUSETTS.

TELEPHONE-TRANSMITTER.

SPECIFICATION forming part of Letters Patent No. 357,452, dated February8 1887.

(No model.)

To all whmn it may concern-.-

Be it known that I, FRANCIS BLAKE, of Weston, in the county of Middlesexand State of Massachusetts, have invented certain Iniprovements inTelephone-Transmitters, of which the following is a specification.

My invention relates tothat class of battery-telephones which arepopularlyknown as transmitters, and refers, especially, to the specieswherein the resistance of a mass of granulatedconducting materialinclosed in a chamber between two conducting-electrodes is varied by thevibrations of a horizontallymounted diaphragm or vibrating plate c011-stituting or supporting one of the said electrodes, the whole beingincluded in the circuit of a voltaic battery. These variations developthe necessary and corresponding changes in the current of the saidbattery, and, passing to any suitable telephonereceiver conductively orinductively, included also in the same circuit, effect therein areproduction of the sound which originally actuated thetransmitting-diaphragm. In the practical operation of thesetransmittersit has been found very convenient to construct them in acompact and portable form which may be readily mounted upon a suitablesupport. It is also advantageous to so construct these instruments thatthe several elements or parts thereof may be interchangeable, wherebywhen any one is out of order it can be replaced with facility byanother, dispensing with the necessity of changing the complete outfit,or even'of removing the ordinary adjustable supporting-arm.

In accordance with these views, the object of my invention is to meetthe above requirements and to consolidate the operative parts of thetransmitter into a simple combination of few elements readily attachableand detachable, perfectly interchangeable, and of such simplicity as torequire no special degree of expertness in its care or management,whileit shall at the same time be easy and economical in construction andrepairs. These objects I achieve by the construction which I shallhereinafter describe; and to this end my invention consists, especially,in the peculiar shape of the different parts of the transmitter, and ina part of this invention, Figure 1 is avertical cross-section of atransmitter showingmy invention. Fig. 2 is a plan view of theinclosing-cap thereof. Figs. 3, 4, 5, and 6 are plan and cross-sectionviews of details. Fig. 7 is a plan view of one form of pendulous or backelectrode; and Fig. 8 is a crosssection (for purposes of comparison) ofthe construction employed tosome extent prior to my invention.

I will. first describe the latter construction.

In the construction shown in Fig. 8, which, as stated, has heretoforebeen experimentally adopted, the operative parts comprise the externalmetallic case, A, having an upward eX- tending circular flange, d,threaded internally near its edge, and having a central aperture in itsbase, which aperture expands into a speaking-tube or mouth-piece, B, thewalls of which may be cast or otherwise madeintegral with the body ofthe case, as in Fig. 8, or which may be separately made and mechanicallyattached thereto, as in Fig. 1. An annular metal plate, 9, faced on itsunder side with insulating material a, and having also a central openingor aperture, is placed within the case and lies upon theinner surface ofthe base thereof, but is not in electrical connecform a seat for theflange of the pendent electrode E, which projects downwardly into thering, and when complete and ready for operation into the granulatedmaterial. An annular plate, 7:, closed at its lower side, with theexception of a central erforation, hasa shoulder cuton theinnersurfaceoftheportion surrounding the said perforation, upon which shoulder thediaphragm is supported, and which aids in forming below the diaphragm anair-space or vocalizing chamber. This plate has a flanged edge threadedwith a female screw, and after the disk of platinum foil constitutingthe vibrating diaphragm is placed upon the flat shoulder cut therein thenon-conducting ring F is screwed down thereon, clamping the edgethereof. The pendent electrode is then seated in the countersink, thegranulated material filled in, and the inelosing cap or cover D, whichhas its flange threaded oirboth outside and inside surfaces, is screweddown upon the insulatingring, as shown, to hold the electrode in place,the inner thread being adapted to engage with the screw on the outsideof the insulating-ring,- while the outer thread is adapted to engagewith a female screw cut on the inner surface of the flange d of themetal frame or external case A. The whole, by means of the externalthread on the outer side of the cap-flange, may then be attached to thestandard transmitter frame or holder, the pendent electrode beingconnected with the circuit through the cap, case,and supportingarm. Thisconstruction hasbecn found unsatisfactory in some respects, it iscomparatively costly and intricate, requires considerable skill and ahigh class of workmanship in manufacture, while the number and necessaryfineness of the screw-threads is disadvantageous, and even with thegreatest care it is a fact that the threads frequently strip, especiallythat one which is cut on the outside of the insulatingring. Moreover, itis most essential that the fragile platinum diaphragm shall be kept freefrom wrinkling, and it has been found that the action of screwing theparts together is apt to wrinkle and otherwise damage the same. Theconstruction I have devised is, on the contrary, severely simple, verycheap, and is held together solely by machine-screws.

I adopt the same general form of outer case, A, and mouth-piece B. Theinclosing-case is bored out true, and has a horizontal flange, F, attheedge of the cavity. A bed-plate, G, (shown in detail in Figs. 3 and 4,)is provided, consisting of a circular perforated metal baseplate, 71,with a shoulder, g, and an upwardlyprojecting flange, t, at its outeredge. A binding-screw, 7:, forming one of the transmitterterniinals, isattached to the plate, and a nonconducting partition, 2, is aiiixed tothe lower face of the said plate for the purpose of insulating it fromthe inclosing-case. The platinum-foil diaphragm i is placed in thisbedplate and seated upon the shoulder g, the v0- calizing-chambcr beingthus formed between lapping the same.

the said diaphragm and the lower part, h, of the base-plate, thecircular perforation of the said plate being the inner termination ofthe mouthpiece or speaking-tube. I provide next a non-conducting ring,f, formed as shown in Figs. 5 and 6, having a shoulder, in, turned tofit snugly in the flange t of the plate G, and being also countersunkatl to form a seat for the pendent electrode E. The lower edge of thisring is inserted in .the cavity of the plate G and clamps the edge ofthe diaphragm without subjecting the same to the twisting or distortingmotion inseparable from a serewcoir nection. The elect-rode E, of anycustomary or suitable construction, may then be inserted, its edge lyingin the seat Z, provided therefor. The variable resistance material beingnew filled in a manner well understood, the entire appliance, as awhole, may be placed in the inclosing case, the binding screw passingthrough the hole at one side of the lloor there of, but being insulatedtherefrom by partition 2. I finally provide a cap-piece, J, fitted'tothe external ease, and having a flange, m, over- This cap makes contactwith the electrode E and connects the same electrically with the metalcase and supporting-arm, and through the said arm with the electriccircuit. It is secured to the flat flange F of the case by any desirednumber of machine-screwsj. I have shown three as being bothconvenientand symmetrical. Small bolts and nuts may of, coursebealternately used,

The outer peripheral boundary of the insulating-ringf, which forms thenon-conducting wall of the inner chamber, is turned to fit exactly thebore of the external case, and it will be seen that by this constructiona compact instrument is very economically furnished, which possesses theseveral advantages I have hereinbefore described.

I do not desire to claim herein any feature relative to the form,character, or position of the electrodes, or the combination of theelectrodes with the resistance-varying medium, as I am aware that thesefeatures are not new. The essence of my invention lies in theconstruction of a skeleton transmitter, the several parts of which areextremely simple, accessible, economical, and easily taken apart and puttogether, the whole being held in place, when put together, by a smallnumber of machine screws or bolts and nuts.

I claiml. The combination, substantially as hereinbefore described, in atelephone-transmitter, of the flanged external case and mouth-pieceattached thereto, the diaphragm-seat mounted therein, but insulatedtherefrom, the non-conducting ring fitted to the innersurface of theinclosing-case, surmounting the said diaphragmseat and adapted to clampthe diaphragm, and the cap-piece attachable to the external case andadapted to hold the several elements to gether by means ofmachine-screws, as specified.

2. In a telephone-transmitter of the class herein specified, the metalexternal case, the insulated diaphragm-seat with circuit-terminalattached thereto, the vibrating diaphragm, the non-conductingclamping-ring adapted to fit within the inclosing-case, and also to theinsulated diaphragm-seat, the pendent or fixed electrode mounted uponthe upper edge of the said non-conducting ring, and the surmounting capin contact with the said electrode and attached to the metalinclosing-case by machine-screws or their equivalents, whereby the partsare securely held in place, and whereby the fixed electrode iselectrically included through the inclosing-case and support in thevoltaic circuit, substantially as described.

3. The combination, in a telephone-transmitter, of the shouldereddiaphragmseat, the diaphragm mounted therein, and the non-c0nductingring accurately fitting the upwardlyprojecting flange of saiddiaphragm-seat and adapted to clamp the edge of said diaphragm and tohold the same in place, and to serve also as the non-conducting sidewall of the 0perating-chamber, as specified herein.

4. In a telephone-transmitter of the class hereinbefore described, theflanged external case, A, and mouth-piece B, combined with thesurmounting cap-piece J, attached to the flange of the said case by themachine-screws j, or their equivalent, as herein specified.

5. The herein-described skeleton transmitter, comprising the externalflanged metal case with mouth-piece attached to the base thereof, thediaphragm-seat adapted to be in the floor of the metal case, butinsulated therefrom, the non-conducting ring or gland fitted inthe'external case and adapted to clamp the dia-

